chore(deps): update dependency gulp-mocha to v6 - autoclosed

[mend-for-github-com[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gulp-mocha	devDependencies	major	^5.0.0 -> ^6.0.0

By merging this PR, the below issues will be automatically resolved and closed:

Severity	CVSS Score	CVE	GitHub Issue
High	9.8	CVE-2021-44906	#55
High	7.5	WS-2021-0638	#62
High	7.1	WS-2018-0590	#2

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Release Notes

sindresorhus/gulp-mocha

### [`v6.0.0`](https://togithub.com/sindresorhus/gulp-mocha/compare/v5.0.0...v6.0.0) [Compare Source](https://togithub.com/sindresorhus/gulp-mocha/compare/v5.0.0...v6.0.0)

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